Violence and fear travel swiftly, and faster still in the era of tweets and status updates and 24-hour rolling news. Just after 2 p.m. on May 22, police answered a call to an incident in Woolwich, southeast London. A 25-year-old soldier, Drummer Lee Rigby, leaving the local barracks, had been hit by a car and then hacked to death in front of horrified onlookers. One of his alleged killers, later identified as Michael Adebolajo, linked the attack to the British military presence in Muslim countries. “We must fight them as they fight us, an eye for an eye, a tooth for a tooth,” he said, waving a bloodied cleaver. Video, filmed by an onlooker, was quickly picked up by news organizations and disseminated on social media.

At 7:15 p.m., a man, reportedly armed with a knife, threw an incendiary device into a small mosque in Braintree, a market town in Essex. At 8:40 p.m., another small mosque in another English market town, Gillingham in Kent, sustained a broken window and damage to a bookcase housing copies of the Koran. Back in Woolwich, the far-right English Defence League (EDL) staged a demonstration against Islam and skirmished with police. In a video posted on the group’s website, its leader Tommy Robinson (also sometimes known as Stephen Lennon and Paul Harris), said “We are at war, and unless you can name the enemy you won’t win that war … The enemy is Islam.” The far-right British National Party is calling for a demonstration against “the wicked and cruel enemy within.”

Since news broke of the Woolwich murder, tensions in Britain have ratcheted up. Scotland Yard has increased the number of officers on patrol. Social-media users were quick to ask whether the May 24 emergency landing of a British Airways jet at Heathrow might be terrorism-related; BA said a technical fault had caused the incident. Mere hours later, Royal Air Force jets escorted a Pakistan International Airlines flight from Lahore away from its intended destination of Manchester, in northern England, to Stansted, near London. Two men were arrested, accused of endangering an aircraft. Shortly after that, one of the capital’s main train stations, London Bridge, was closed amid reports on social media of a man wielding an ax; and the M6 motorway, a main arterial route in central England, was shut while police investigated a suspicious vehicle. There were few details and no clarity yet on any of the incidents, but in the febrile atmosphere after Woolwich, it’s all too easy to see links where there may be none. And there has been an upsurge in small acts of aggression. The Tell MAMA hotline, which normally takes three or four calls a day reporting Islamophobia in various forms, has logged 72 incidents. British Muslims feel “a real endemic fear now,” says Fiyaz Mughal, coordinator of Tell MAMA and a director of an interfaith organization called Faith Matters. “It really is quite deep. Muslims have a fear that their institutions like mosques may be under potential attack. And they have a sense that unfortunately something nasty may happen.”

Brooks Newmark, the Conservative MP who represents Braintree, e-mails that “the tension is palpable especially amongst the Muslim community in our town. They wholly condemned the brutal murder that took place in London only hours before [the mosque attack]. They said the men who carried out the vile acts in London do not represent a vision of Islam that they believe or even recognize. But they are wondering what they can do to heal wounds that they did not cause.” He adds: “We have a small Muslim community in Braintree, who are well integrated. They are shopkeepers, restaurant owners and doctors. They are respected members of our community. There was a sense of shock and disbelief when our small town hit the headlines the same day as the brutal murder of a British soldier by Islamic radicals. How could someone in our community connect the dots between the vile actions of two fundamentalists 50 miles [80 km] away in London with the peaceful small Muslim community in our town?”

That question, about how the dots get connected — and how to stop dangerous distortions emerging when they do — is a key concern for the British authorities as they continue to focus on solving the primary crime, Rigby’s brutal slaying, and to make sure that his murder was not part of a broader terrorist campaign. They have released few details about the two men arrested at the scene of the murder, both of whom have been hospitalized after being shot by police, but the second Woolwich suspect is reported to be Michael Adebowale, a 22-year-old from nearby Greenwich. More information has emerged about Adebolajo, the 28-year-old suspect filmed with a cleaver, and his alleged association with Anjem Choudary, the former leader of al-Muhajiroun. The group came into notoriety in 2003 for organizing an anniversary celebration of the 9/11 attacks and was banned the following year under British antiterrorism legislation. Links between the group and its offshoots and a significant number of British terrorist plots, including the 7/7 bombings in London, coordinated suicide attacks that claimed 56 lives (including the lives of the four bombers themselves), illustrate how easily the contagion of hatred spreads — whether that hatred stems from the misappropriation of the name of Islam or the fear of Islam.

Politicians from Britain’s mainstream parties have joined forces in calling for calm after Woolwich. “After an event like this it is natural that questions will be asked about what additional steps can be taken to keep us safe,” said Prime Minister David Cameron. “I will make sure those questions are asked and answered, but I am not in favor of knee-jerk responses. The police have responded with heightened security and activity, and that is right. But one of the best ways of defeating terrorism is to go about our normal lives, and that is what we shall all do.”

Nigel Farage, leader of the U.K. Independence Party (UKIP), a fringe party whose fast-rising popularity is fueled in part by robust anti-immigration policies, also put out a statement: “I hope and believe that this is an isolated incident and appeal for calm amongst all our communities.” Speaking at a May 24 event at London’s Foreign Press Association, he rejected the suggestion that UKIP’s rhetoric risks feeding the hostilities behind the mosque attacks and far-right protests. He singled out the “cowardice of the British establishment” in failing to curb the influence of radical preachers. “We have been turning a blind eye to hate preachers, turning a blind eye to polygamy, turning a blind eye to Shari‘a law in British cities,” he said. He told TIME that more unrest could be expected from Britain’s far right over the coming holiday weekend. “They’ll all be on the booze. They’ll all be on the streets. It will be ugly,” he said.

There has been no shortage of ugliness on British streets in the past days, and the ugliest moment of all came in Woolwich when a young soldier fell victim to a toxic idea. But the very spot where he died has also sprouted a strange loveliness, as friends and strangers, moved by his story, leave flowers and messages and other tributes. The makeshift memorial, and a quiet determination not to let extremism win the argument, continues to grow.